The present invention relates to a method of and a system for underground irrigation, and more particularly to such method and system which enable constant supplying of water in the amount required by cultivated plants to their root portions without waste of water.
In order to irrigate various plants such as crops, flowers and fruits, it has been a common practice to install a number of sprinklers over the cultivation field to sprinkle water from above the soil. Though this method has been satisfactory in its simpleness of installation, use and maintenance, it also has some drawbacks in that it requires an extremely large amount of water to sufficiently dampen the cultivation soil to thereby supply a sufficient amount of water to the roots of the cultivated plants, because water is sprinkled over a wide area including the portions of the land where the dampening is not required and because the loss of water by evaporation is large, and that the sprinkling of water during the time of flowering of the plants affects the fructification of the cultivated plants. The waste of water as stated above is against the effective use of the water resources and should be eliminated as much as possible.
In view of the aboves, in order to dampen only the necessary portion of the soil with a smaller amount of water, a drip irrigation system has been developed. This irrigation system comprises a water feed pipe connected to a water supply source and installed on the ground and drip units suitably connected to the water feed pipe. According to this system, water may be supplied only to desired places so that waste of water is reduced. This irrigation system, however, has also a drawback that the evaporation of water is inavoidable because the water is supplied from above the land so that more water than required by the cultivated plants has to be dripped from each drip unit. Furthermore, the amount of water dripped from the drip units located far from the water supply source is smaller than that dripped only from the drip units located closer to the water supply source since the water pressure in the water feed pipe drops toward the remote end of the pipe. Therefore, if the water pressure is increased to sufficiently dampen the soil far from the water supply source, the soil close to the water supply source is excessively dampened. This results in waste of water and also affects the desired growth and quality of the cultivated plants. Furthermore, since the dripping units, generally, are placed on the cultivation soil, it often happens that the earth, fertilizer and other matters adhere to the water outlet of the dripping unit to clog the same, resulting in under-feed of water. Still further, since the stem and leaves of the cultivated plant are wet by the water as dripped from the drip unit and are normally placed in an environment of high humidity caused by the evaporation of water, the propagation of bacteria is promoted so that the growth of the cultivated plant is considerably retarded and sometimes the plants are withered. Furthermore, the drip irrigation system requires pump means to drip water from the drip units.